If you're using the stock harness and computer and want to do it yourself you need to get a pin out of your PCM and thin out what you don't need. Its not that hard and increases your knowledge of the system ten-fold. I would recommend everyone do it but some people just don't care to and I understand that, too. My ECM is probably different than yours but here is a spreadsheet of mine. You can learn from it to do yours.
http://www.patooyee.com/ls2build/harness/Harness Info.pdf
There is also a bunch of info at
http://www.lt1swap.com/ their pin-out may match yours.
PS, if you do your own harness, keep all the wires and try not to cut them. Over half the entire harness comes out and I had enough left over to do almost my entire chassis harness with. It is good, high quality wire, too. I ought $300 worth of new wire in anticipation of doing my chassis and ended up only using about $10 worth of it. And my chassis harness is not simple, either. I have lots of stuff in it that most rigs don't.